An electrochemical cell packaging material composed of a multilayer film has recently been used as an exterior body for electrochemical cells such as lithium ion batteries, lithium polymer batteries, and fuel cells, or liquid capacitors, solid capacitors, and double-layer capacitors which include liquid, solid ceramic, organic, or other dielectrics, as described in Patent Citation 1, for example.
FIG. 4 is a sectional view showing the layer configuration of the conventional electrochemical cell packaging material, and as shown in FIG. 4, the conventional electrochemical cell packaging material 110 is composed of at least a base layer 111, a metal foil layer 112, and a heat-sealable layer 115, wherein the base layer 111 and the metal foil layer 112 are bonded via an adhesive layer 113, and the heat-sealable layer 115 and the metal foil layer 112 are bonded via an acid-modified polyolefin layer 114.
FIG. 5A is an exploded perspective view showing a lithium ion battery that uses a conventional embossed-type exterior body, and FIG. 5B is a perspective view showing a lithium ion battery that uses the conventional embossed-type exterior body. As shown in FIGS. 5A and 5B, a lithium ion battery 121 is fabricated by placing a lithium ion battery body 122 in a tray 120a having a concave part formed by cold pressing the electrochemical cell packaging material 110 shown in FIG. 3 and blocking the open part of the tray 120a with a sheet 120b in a cold press forming step, and overlaying the tray 120a with the heat-sealable layer 115 of the sheet 120b and heat-sealing the edge thereof in a sealing step.
In a lithium ion battery 121 fabricated in this manner, in the final battery manufacturing step, a label indicating product information and the like is affixed to the surface of an exterior body 120, or product information and the like is printed by an inkjet directly on the surface of the exterior body 120 instead of using a label.
However, in a case in which a counterfeit lithium ion battery or electrochemical cell packaging material from a manufacturer other than the authorized manufacturer bears the same identification mark as that of an authorized manufacturer, it is difficult to distinguish between a genuine product and a counterfeit product.